The present invention relates to an open-end spinning rotor having a rotor shaft and a rotor cup which are detachably connected via a coupling device for removal of the rotor cup while the rotor shaft remains supported in the spinning-rotor bearing.
Most open-end rotor spinning machines currently used in the textile industry have spinning rotors that are supported by their rotor shaft in the bearing nips of a so called support disk bearing assembly and are driven by a tangential belt running the length of the machine. These spinning rotors customarily have the rotor shaft and the rotor cup connected in an almost undetachable manner via a force or press fit. Thus, the spinning rotor assembly of the rotor cup and rotor shaft can be inserted or removed as required, e.g., when worn, from the front of the spinning station through the opened rotor housing.
Moreover, spinning rotors are also known, e.g., from European Patent Publication EP 0 972 868 A2, that are driven by an individual motor and are supported by their rotor shaft in a magnetic bearing arrangement. This magnetic bearing arrangement consists of a front and a rear bearing position that have permanent magnetic rings axially opposite each other. One of these permanent magnetic rings is fastened to the stator of the motor whereas the other permanent magnetic ring rotates with the rotor shaft.
Since the insertion or removal of spinning rotors supported in this manner requires a not insignificant assembly cost, the rotor cup is detachably connected to the rotor shaft in these spinning rotors. That is, the rotor cup can be removed or replaced as required, e.g., when worn or during a batch change, after the loosening of a screw connection without the rotor shaft also having to be removed thereby.
However, the detachable coupling of the rotor shaft and rotor cup by means of a screw connection is not totally satisfactory. It can not always be assured in the case of such screw connections that the rotor cup and the rotor shaft remain sufficiently firmly connected at every point in time, e.g., in particular over the course of rather long running times. In addition, it can be relatively complicated and time-consuming to screw the rotor cup fast to the rotor shaft while the latter remains supported in the magnetic bearing.
In addition to the previously described screw connection, numerous other embodiments of devices for coupling a rotor cup to a rotor shaft are known from the patent literature that make possible a detachable connecting of the rotor cup to the rotor shaft. For example, German Patent Publication DE 38 15 182 A1 describes various coupling variants with a positive or non-positive fit that are intended to assure an unobjectionable and readily detachable fixing of the rotor cup to the rotor shaft. However, the individual coupling variants are, as a whole, constructed in a rather expensive manner and are therefore relatively costly.
A comparable coupling device that is significantly simpler in its construction is described in European Patent Publication EP 0 808 923 A1. This known coupling device is designed in the manner of a clip connection in which one part of the clip connection is arranged on the rotor cup and the other part on the rotor shaft. At least one part of the clip connection is loaded by an elastic element.
Even in the case of the coupling device according to European Patent Publication EP 0 808 923 A1 the replacement of the rotor cup is at least complicated, especially when the rotor shaft remains inserted in the bearing device during this replacement. In addition, this coupling device does not always ensure that the rotor cup will always remain reliably fixed to the rotor shaft even at high speeds of the spinning rotor, particularly after repeated insertions and removal of the rotor cup.
Other coupling devices are known from German Patent Publications DE 38 35 037 A1 and DE 196 18 027 A1. German Patent Publication DE 38 35 037 A1 relates to a mechanical, hydraulic tensioning device with a thin-walled, expandable casing that can be tensioned between the rotor shaft and the rotor cup. German Patent Publication DE 196 18 027 A1 describes a centrifugal-force coupling, i.e., a special coupling element comprises spring-loaded spheres that are pressed outward during the operation of the spinning rotor as a consequence of centrifugal force and fix the rotor cup thereby to the rotor shaft. These coupling devices are also
quite expensive in design and in addition require a high balancing precision on account of the high rotor speeds, which renders the manufacture of such devices quite expensive.